This invention relates to a device for hinging a barrel in an air-powered carbine or gun having a tiltable barrel, in which some of its composing elements are moulded in plastic material.
In prior art, air-powered carbines or guns are known in which the barrel is tiltable with the double aim, on one hand, to make the back end of the barrel accessible for facilitating its loading with ammunition, and on the other hand, for using the tiltable barrel itself as a lever arm for loading a thrusting spring of a plunger of an air pressure compression chamber. This tiltable barrel requires accurate hinging means and centring and locking means for the barrel in closed position securing the alignment of the bore of the said barrel with an outlet of compressed air from the said pressure chamber. The said hinging, centring and locking means involve a series of complex configurations which have to be shaped by mechanising them when the basic plates are of metal, namely steel, which means very high production costs.
EP-0 467 819, granted to this applicant, discloses improvements provided to an air-powered carbine or gun having a tiltable barrel consisting in grouping the said complex configurations into two subassemblies which can be made by moulding, typically by plastic injection moulding, cutting down thus the production costs. One of the said subassemblies is attached integral with the barrel rear part by simple coating moulding, coating at same time the whole of the said barrel. The other subassembly constitutes a fork and it is formed by an independent part made in a single moulding operation and is designed to be attached integral with the pressure chamber front part by tight insertion locked by means of pins. For this aim, this second subassembly comprises a cylindrical part which is designed to be inserted in the pressure chamber front part, and a part which configures the said fork with holes for a hinging pin with respect to the first subassembly integral with the barrel.
Although this kind of moulding construction allows lower production costs, it still has some drawbacks which ask for a solution. As for the first subassembly, the fact of carrying out a coating moulding on the whole of the barrel length requires very large-sized moulds and providing a great amount of moulding material, which is still meaning a high production cost. As for the second subassembly, the whole of the plastic part forming the said fork is overhanging with respect to the metal tube forming the pressure chamber, showing a transition neck between the said fork part and the cylindrical part inserted in the said metal tube. Stresses produced in the material because of repeated efforts tends to be concentrated in this neck or transition area therefore the part can be bent or even broken at this point due to fatigue.
Therefore, the object of this invention is to provide a hinging device for a barrel in an air-powered carbine or gun having a tiltable barrel which comprises complex configurations grouped in two groups which can be obtained by moulding, and that the production is less expensive and more strong than the hinging devices of the prior art.
This object is achieved, according to this invention, providing a hinging device for a barrel in an air-powered carbine or gun having a tiltable barrel of the kind comprising a barrel box integral with the barrel rear end, the said barrel box comprising a hole for a hinging pin and a latch designed respectively for hinging and closing the barrel in a fork integral with the front end of an air pressure chamber, the said barrel box being connected to a mechanism of hinged levers adapted for compressing a thrusting spring of a plunger of the pressure chamber, using for this the barrel as a lever arm when it is lowered. The device of this invention is characterized in that the said fork comprises an internal fork part, obtained by moulding, preferably of a plastic material provided with two front branches and a rear end portion tightly inserted and joined in a portion of mouth of the said pressure chamber, which in turn is forwardly extended in two side blades which are arranged closely covering the said two front branches of the said internal fork part.
With this arrangement it is achieved to concentrate in the said internal fork part obtained by moulding, all the more complex configurations, such as the said front branches, holes for the pins, at least one external perimetric slot for containing an annular sealing element, a longitudinal hole for the passage of the air from the pressure chamber, a retaining configuration for the said latch with the barrel at a closed position, among others, while the branches of the fork remain covered and externally strengthened by the said side blades of the said portion of mouth of the pressure chamber, which are obtained by simply cutting the metal tubular material itself of which the pressure chamber is an integral part. The said mouth portion includes other characteristics which in every case are simple holes easy to mechanise. In addition, from the internal fork part moulded in plastic material any neck shape disappeared which could concentrate stresses in a maximum bending area, as it occurred in the device of the said document EP-0 467 819.
On the other hand, the device of this invention provide a barrel box obtained by moulding, preferably by injection moulding a plastic material, embedding the barrel rear portion as an insert. Thus, the said barrel box obtained by moulding comprises those complex configurations such as holes for pins, notches, a longitudinal recess, open at the rear part, for slidingly housing the said latch and in addition also an anchoring configuration for an adjustable rearsight, while at the said rear portion of the barrel, it only includes some planes on its external surface easy to mechanise. The fact of only injecting the barrel box on the barrel rear portion as an insert, without fully coating the whole of the barrel length, as it occurs in the device of document EP-0 467 819, allows to obtain results equivalent with very smaller sized moulds and with less plastic material being used and therefore a lower cost.